Never, ever use something like this.Since the private key was generated by a 3rd party, it must be considered compromised.
NEVER use a private key that wasn't generated on your own computer! THIS IS NOT A COLD WALLETIt's a good thing he didn't post the registered account name, because this has led you to post here, and see this warning.
If you really want a cold storage solution, please follow these instructions:
http://docs.bitshares.org/bitshares/user/security-cold.htmlI would do a test run first, following instructions, depositing funds into the cold wallet address, adding the key to a hot wallet, and finally transferring the funds to a different account to confirm that you still have access. Once you are confident, you can do it for real.
Sorry this is so complicated, but it's the best option we have right now.